Some way or other, originally, we are all Krsna conscious, pure…  We cannot ascertain when this transformation took place. There is no necessity of making research how we fell in this material contamination or envelopment. But we should be intelligent enough to understand that we are fallen now. How we fell — you can trace out the history, but it is very difficult because anadi karama-phale, nobody can ascertain. Just like when a man is diseased he goes to doctor. So when he goes to the doctor, the doctor gives him medicine according to the symptoms and the diagnosis. There is no necessity of find out the history, how he fell diseased. There is history, but that is not possible to trace out.

From Srila Prabhupada's lecture on Srimad-Bhagavatam 3.26.23-4 — Bombay, January 1, 1975